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POPULAR SCIENCE REVIEW. 
from tlie coal-measures to the mountain limestone. These latter 
are themselves conformable, and have in this area been together 
upheaved and bent into a fold or “ anticlinal,” and the summit 
of it worn away before the newer secondary rocks were depo- 
sited. The accompanying horizontal section, taken along the 
line marked on the map, will show the general aiTangement of 
the rocks. It is the knowledge of an anticlinal like this which 
leads to the inference that coal occurs on the south of the 
Mendips, where it is not actually seen nor has yet been proved. 
The coal comes to the surface on the north of this range of hills, 
and is there largely worked ; while, on the south of the anti- 
clinal, as represented in the section, the coal-measures occur 
again, though they are entirely concealed at the surface by the 
overlying Secondary deposits. Such a conclusion shows us one 
of the practical bearings of geology. 
A study of the science will enable us to point out not only 
where the coal-measures exist at the surface, but generally with 
great confidence those areas where coal cannot exist, and also 
to estimate the probability of its existence beneath those rocks 
which were formed subsequently to it. Thus it is that coal is 
considered as likely to occur in the south-eastern counties of 
England, beneath the tertiary and secondary rocks of that area ; 
it being considered that there is a thinning out of the rocks 
which normally occur between the cretaceous beds and the 
coal, so that it might be reached at a reasonable depth. 
In our section we find that a slight “ fault ” or disturbance 
affects the older rocks, and has shifted and let down those on 
its southern side. This shows more plainly on the map, as in 
consequence of it the outcrop of the Millstone Grrit has been 
considerably modified. The phenomena exhibited in the section 
show that there are many important considerations to affect our 
ideas of the rocks at some depth below those coloured on our 
maps. Though the series has a regular arrangement, many 
rocks may be absent in places, and the older ones affected by 
denudation and disturbance before the newer ones were deposited 
upon them ; so that in mining and well-sinking the opinion of 
the geologist is very necessary. It is astonishing that even now- 
a-days so many attempts are made to find coal in places where 
a geologist would at once discern there could be no chance of 
getting it. Two years ago we came across a shaft which was 
being sunk in the lower limestone shales of the Mendips, and 
had indeed just reached the old red sandstone, two or three 
thousand feet below the coal-measures, which had been denuded 
off! 
The chief economic uses of geological maps are to point 
out the localities where may be found limestone for building 
purposes and to be burnt for lime ; sandstones and grits, fit for 
